JP7159111B2 - Combination of sliding member and lubricating oil - Google Patents

Description

TECHNICAL FIELD The present invention relates to a combination of a sliding member having a coating film excellent in low-friction performance on its sliding surface and lubricating oil used during sliding.

In recent years, as automobile engines, which are internal combustion engines, have become lighter and more powerful, sliding members that are used under severe sliding conditions, especially piston rings used in internal combustion engines, are required to operate under severe high-temperature and high-pressure environments. Further improvement in wear resistance and the like is required because it is used in For example, since the outer peripheral sliding surface of a piston ring is in sliding contact with the inner peripheral surface of a cylinder liner, particularly excellent wear resistance is required. A film or the like is used. In order to meet the above requirements, the outer peripheral sliding surface and upper and lower surfaces of the piston ring are coated with a chromium plating film, a nitriding treatment film, chromium nitride (CrN, Cr ₂ N) produced by the PVD method, and titanium nitride ( A hard film such as TiN) is formed.

However, with the recent trend toward lighter weight and higher output of internal combustion engines, piston rings are used under even more severe conditions. Therefore, a sliding member having excellent toughness and wear resistance is desired. In addition, in recent years, lubricating oils have become less viscous due to lower friction, and as a result, the scuffing resistance has deteriorated, so the Mo content has increased. Development of hard coatings that are compatible with lubricating oils is desired.

In response to such a request, for example, Patent Document 1 proposes a sliding member coated with a hard film having improved sliding properties, particularly peeling resistance. In this technique, the outer peripheral surface of the piston ring is coated with a hard coating by arc ion plating. range, and the Cr content is 30 to 49 atomic %.

Further, Patent Document 2 proposes a sliding member coated with a film that is excellent in wear resistance, scuffing resistance, and properties that do not increase the wear of the mating member (aggressiveness to the mating member). In this technique, the outer peripheral surface of a sliding member is coated with a Cr--V--B--N alloy film, and the Cr--V--B--N alloy film is formed by a physical vapor deposition method, especially an ion plating method. , a vacuum deposition method or a sputtering method, and has a V content of 0.1 to 30% by weight and a B content of 0.05 to 20% by weight.

Further, Patent Document 3 proposes a sliding member on which a Cr--B--Ti--N alloy film having excellent wear resistance and scuff resistance is formed. This technology is a piston ring composed of a base material, a nitride layer and a Cr-B-Ti-N alloy film, and the Cr-B-Ti-N alloy film is formed by the PVD (physical vapor deposition) method. The outer peripheral sliding surface (corresponding to the sliding surface) of the nitride layer is coated with 0.05 to 10.0% by mass of B, 5.0 to 40.0% by mass of Ti, and 10.0 to 30.0% by mass of N. It contains 0% by mass and the balance is Cr.

Further, Patent Document 4 proposes a piston ring having higher wear resistance, crack resistance and peeling resistance. This technology is a piston ring whose sliding surface is coated with a Cr--B--V--N system alloy film, and has a B content in the range of 0.1% by mass or more and 1.5% by mass or less. The V content is in the range of 0.05% by mass or more and 1% by mass or less, and the [B content/V content] is in the range of more than 1 and 30 or less.

JP-A-2001-335878 JP-A-2000-1767 JP 2006-265646 A WO2016/002810

However, the above patent documents 1 to 4 are insufficient to satisfy the high wear resistance demanded in recent years. In recent years, internal combustion engines have become lighter and more powerful, and under severe conditions, the temperature is higher and boundary lubrication is likely to occur. In addition, low friction properties are required.

In response to these demands, the present inventors have improved low-friction performance by combining a lubricating oil with a specific composition and a coating film with a specific composition in the sliding phenomenon under lubricating oil like in an actual internal combustion engine. It was found that it is possible to improve the wear resistance performance by increasing the The present invention has been made based on the above findings, and an object of the present invention is to combine a sliding member having a coating film excellent in low friction performance on the sliding surface and lubricating oil used during sliding. is to provide

A combination of a sliding member and lubricating oil (first embodiment) according to the present invention is a combination of a sliding member and lubricating oil used when the sliding member slides, wherein the sliding member A Cr—B—(Mn, Mo)—N-based alloy film is provided on the moving surface, and the alloy film contains one or both of the Mn and Mo, and the content of the Mn and the Mo is The total is within the range of 2% by mass or less, and the lubricating oil is characterized by containing Mo.

A combination of a sliding member and lubricating oil (second embodiment) according to the present invention is a combination of a sliding member and lubricating oil used when the sliding member slides, wherein the sliding member A Cr—B—(Mn, Mo)—N-based alloy film is provided on the moving surface, and the alloy film contains at least Mo among the Mn and Mo, and the content of the Mn and the Mo is The total is within the range of 2% by mass or less, and the lubricating oil is characterized by not containing Mo.

According to the first and second aspects of the invention, the Mn and Mo contained in the alloy film can be made different depending on whether or not the lubricating oil contains Mo. That is, when the lubricating oil contains Mo, the alloy film should contain one or both of Mn and Mo. On the other hand, when the lubricating oil does not contain Mo, the alloy film contains at least Mo. By doing so, it is possible to generate a tribofilm made of molybdenum disulfide on the sliding surface during sliding due to the composition of the lubricating oil and the composition of the alloy film, thereby improving the low friction performance and the wear resistance performance. can be improved.

In the combination of the sliding member and the lubricating oil according to the present invention, the B content is in the range of 0.1% by mass or more and 1.5% by mass or less, and the N content is 30% by mass or more and 40% by mass. It is within the range of mass % or less, and the balance is preferably the above-mentioned Cr and unavoidable impurities.

The combination of the sliding member and the lubricating oil according to the present invention further contains V and Ti, the V content is in the range of 0.05% by mass or more and 1% by mass or less, and the Ti content is preferably in the range of 0.05% by mass or more and 1.5% by mass or less.

In the combination of the sliding member and lubricating oil according to the present invention, it is preferable that the sliding member is a piston ring for an internal combustion engine.

According to the present invention, a sliding member provided with a coating film excellent in low friction performance on the sliding surface and sliding, which can be preferably applied under severe conditions accompanying further weight reduction and higher output of internal combustion engines in recent years. Combinations with occasional lubricating oils can be provided.

1 is a schematic cross-sectional view showing an example of a piston ring for an internal combustion engine, which is a sliding member according to the present invention; FIG. FIG. 4 is a schematic cross-sectional view showing another example of a piston ring for an internal combustion engine, which is a sliding member according to the present invention; It is a configuration principle diagram of a nano scratch tester used in the measurement of the friction coefficient, (A) is a measurement mode on a sliding surface, and (B) is a measurement mode on a non-sliding surface. FIG. 3 is an explanatory diagram showing the SRV test performed before measurement with the nanoscratch tester shown in FIG. 3 and the subsequent processing procedure, (A) is the state during the SRV test, and (B) is the state after the SRV test. There is, and (C) is a mode in which the lubricating oil is removed. It is explanatory drawing of a roller-tip type|mold abrasion test method. FIG. 2 is a configuration principle diagram of a scratch tester used for evaluation of toughness. 10 is a graph showing the results of a nano-scratch test of the alloy film of Example 4 using a lubricating oil containing Mo. FIG. 4 is a graph showing the results of a nano-scratch test of the alloy film of Example 4 using a lubricating oil that does not contain Mo. FIG. 4 is a graph showing the results of a nano-scratch test on the alloy film of Comparative Example 1 using a lubricating oil containing Mo. FIG. 10 is a graph showing the results of a nano-scratch test on the alloy film of Comparative Example 2 using a lubricating oil containing Mo. FIG. 10 is a graph showing the results of a nano-scratch test on the alloy film of Comparative Example 3 using a lubricating oil containing Mo. FIG. It is explanatory drawing of adsorption force measurement by AFM (atomic force microscope). It is a graph which shows an adsorption force measurement result.

A combination of a sliding member and lubricating oil according to the present invention will be described with reference to the drawings. The embodiments shown below are examples of the present invention, and the technical scope of the present invention is not limited to the following embodiments. In addition, since it demonstrates using the piston ring for internal combustion engines as a sliding member below, a sliding member is read as a piston ring and demonstrated.

As shown in FIGS. 1 and 2, the combination of the sliding member and lubricating oil according to the present invention includes the sliding member 10 (10A, 10B, 10C) and the lubricating oil used when the sliding member 10 slides. It is a combination with oil 56. As a combination according to the first embodiment, the sliding member 10 has a Cr—B—(Mn, Mo)—N-based alloy film 3 provided on the sliding surface 11, and the alloy film 3 includes Mn and One or both of Mo is included, the total content of Mn and Mo is within a range of 2% by mass or less, and the lubricating oil 56 contains Mo. As a combination according to the second embodiment, the sliding member 10 has a Cr—B—(Mn, Mo)—N-based alloy film 3 provided on the sliding surface 11, and the alloy film 3 includes Mn and At least Mo is contained in Mo, the total content of Mn and Mo is within a range of 2% by mass or less, and the lubricating oil 56 does not contain Mo.

According to the combination of the sliding member 10 and the lubricating oil 56 according to the first and second embodiments, Mn and Mo contained in the alloy film 3 differ depending on whether the lubricating oil 56 contains Mo. can do. That is, when the lubricating oil 56 contains Mo, the alloy film 3 contains one or both of Mn and Mo. On the other hand, when the lubricating oil 56 does not contain Mo, the alloy film 3 is It is configured to contain at least Mo. By doing so, it is possible to generate a tribofilm made of molybdenum disulfide on the sliding surface 11 during sliding due to the composition of the lubricating oil 56 and the composition of the alloy film 3, thereby improving the low friction performance. Wear resistance performance can be improved. Such a sliding member 10 can be used as various piston rings, and is particularly preferably used as a top ring, an oil ring, and the like.

Hereinafter, constituent elements of the sliding member 10 will be described by taking a piston ring for an internal combustion engine (hereinafter denoted by reference numeral 10) as an example.

(Base material)
As the base material 1, various types of materials used as the base material of the piston ring 10 can be used, and the material is not particularly limited. For example, various steel materials, stainless steel materials, casting materials, cast steel materials, etc. can be applied. Among these, for example, martensitic stainless steel, spring steel chromium manganese steel (JIS SUP9 material, ISO 55Cr3 material, AISI 5155 material), chromium vanadium steel (JIS SUP10 material, ISO 51CrV4 material, AISI 6150 material), silicon Chromium steel (JIS SWOSC-V material, DIN 17223/2-90), high carbon chromium bearing steel (JIS G4805, SUJ2 steel), 10Cr steel and the like can be preferably mentioned. The base material 1 can also be called a base material.

The substrate 1 may be pretreated as necessary. Examples of the pretreatment include a treatment for adjusting the surface roughness by polishing the surface. The adjustment of the surface roughness can be exemplified by, for example, a method of lapping the surface of the substrate 1 with diamond abrasive grains and polishing the surface.

(Underlayer)
The underlayer 2 of the alloy film 3 is provided on the substrate 1 as necessary. Examples of the underlayer 2 include a metal underlayer (see FIG. 1B) and a nitriding layer (not shown). These underlayers 2 can be provided at arbitrary locations according to their types. For example, the base layer 2 may be formed only on the outer peripheral sliding surface 11 where the piston ring 10 contacts and slides on a cylinder liner (not shown), or may be formed on other surfaces such as the upper surface 12 of the piston ring 10, It may be formed on the lower surface 13, and may be formed on the inner peripheral surface 14 as necessary.

For example, when stainless steel is applied as the base material 1, the nitriding layer is formed by diffusing nitrogen into the surface of the stainless steel and forming a hard nitrided layer as a base layer. The nitriding layer is preferably used as a base layer for piston rings. The nitriding treatment can be performed by a conventionally known method. Although the thickness of the nitriding layer is not particularly limited, it is preferably in the range of 3 μm or more and 50 μm or less.

The metal underlayer can include a metal layer such as titanium or chromium. The underlying metal layer of titanium, chromium, or the like can be formed by various film forming means, for example, film forming means such as vacuum deposition, sputtering, and ion plating can be applied. Although the thickness of the metal underlayer is not particularly limited, it is preferably in the range of 0.1 μm or more and 2 μm or less.

(alloy film)
As shown in FIGS. 1 and 2, the alloy coating 3 is provided on the base material 1 or on the base layer 2 when the base layer 2 is provided on the base material 1 . The alloy film 3 is preferably provided at least on the outer peripheral sliding surface 11 of the piston ring 10 (10A, 10B, 10C, 10D). At least the outer peripheral sliding surface 11 of the piston ring 10 is provided with the alloy film 3 because the outer peripheral sliding surface 11 of the piston ring 10 comes into contact with the mating member, the cylinder liner, when the piston slides. By providing this alloy film 3 at least on the outer peripheral sliding surface 11, the alloy film 3 may be formed on the upper surface 12 and the lower surface 13, which are surfaces other than the outer peripheral sliding surface 11, and furthermore, if necessary It may be formed on the inner peripheral surface 14 .

The alloy film 3 is a Cr--B--(Mn, Mo)--N system alloy film. That is, the Cr--B--(Mn, Mo)--N system alloy film 3 is a ternary system Cr--B--N alloy film and further contains one or both of Mn and Mo. It is a quinary alloy film. Therefore, this alloy film 3 includes a ternary Cr--B--N alloy film containing only Mn, one containing only Mo, and one containing both Mn and Mo.

This alloy film 3 may be a Cr--B--V--Ti--(Mn, Mo)--N system alloy film 3 further containing V and Ti in order to improve toughness and wear resistance. That is, the quinary Cr--B--V--Ti--N alloy coating may be further a hexanary or 7-ary alloy coating 3 containing one or both of Mn and Mo. Therefore, the quinary Cr—B—V—Ti—N alloy film may contain only Mn, may contain only Mo, or may contain both Mn and Mo. may be Inevitable impurities may be contained in the alloy within a range that does not hinder the effect of the alloy film 3 .

The present invention improves the low friction performance by combining the lubricating oil 56 with a specific composition and the coating film (alloy film 3) with a specific composition in the sliding phenomenon under lubricating oil like in an actual internal combustion engine. It was completed by discovering that it is possible to improve the wear resistance performance by increasing the wear resistance. As can be understood from the test results of Examples and Comparative Examples described later, in sliding under lubricating oil, Mn and Mo contained in the alloy film 3 differ depending on whether the lubricating oil contains Mo. found that it can be done. That is, when the lubricating oil 56 contains Mo, the alloy film 3 may contain one or both of Mn and Mo. On the other hand, when the lubricating oil 56 does not contain Mo, the alloy film 3 contains at least Mo. By doing so, it is possible to generate a tribofilm made of molybdenum disulfide on the sliding surface 11 during sliding due to the component composition of the lubricating oil and the component composition of the alloy film, thereby improving the low friction performance and the wear resistance. It can improve performance.

The reason why the alloy film 3 need only contain one or both of Mn and Mo in the case where the lubricating oil 56 contains Mo is that Mo and the sulfur component contained in the lubricating oil This is because a tribofilm made of molybdenum disulfide can be generated on the surface of the alloy film 3 during sliding. In this case, although the alloy film 3 does not necessarily contain Mo, it is preferable that the alloy film 3 also contains Mo, because it facilitates the formation of the tribofilm. Moreover, regardless of whether the alloy film 3 contains Mo, it is preferable to contain one or both of Mn and Mo because the wear resistance can be improved. Therefore, when the lubricating oil 56 contains Mo, the alloy film 3 does not necessarily contain Mo, but preferably contains Mo.

It should be noted that the alloy film 3 containing B, such as the Cr—B—N alloy film 3 of Comparative Example 2, which will be described later, has a higher molybdenum disulfide content than the Cr—N alloy film of Comparative Example 1, which does not contain B. It is considered that the tribofilm composed of is likely to be generated on the surface of the alloy film 3. Therefore, the alloy film 3 constituting the present invention is a ternary Cr—B—N alloy film and a quaternary or quinary alloy film 3 containing one or both of Mn and Mo. be.

Moreover, when the lubricating oil 56 does not contain Mo, it is desirable that the alloy film 3 always contains Mo. The reason is that Mo contained in the alloy film 3 and the sulfur component of the lubricating oil 56 generate a tribofilm made of molybdenum disulfide on the surface of the alloy film 3 during sliding. In this case, the alloy film 3 may contain only Mo, or may contain both Mn and Mo, as described above.

A "tribofilm" is known to be a film formed by the adsorption or chemical reaction of an additive contained in a lubricating oil on the surface of a friction member. The present invention is characterized by a combination (a combination of a sliding member and a lubricating oil) that easily forms a tribofilm made of molybdenum disulfide on the surface of the alloy film 3 . As means therefor, a Cr—B—N alloy film 3 containing B, which easily forms a tribofilm, is added to the Cr—N alloy film, and one or both of Mn and Mo, which are advantageous for improving wear resistance, is added. are included. As for "one or both of Mn and Mo", when the lubricating oil used in the sliding environment contains Mo, the Cr—B—(Mn, Mo)—N-based alloy film 3 does not necessarily contain Mo. Although not essential, it preferably contains Mo, and when the lubricating oil used in the sliding environment does not contain Mo, the Cr—B—(Mn, Mo)—N-based alloy film 3 always contains Mo. It is characterized in that it is configured to be

Since the lubricating oil is based on mineral oil, it contains a sulfur component that forms a tribofilm made of molybdenum disulfide. A commonly used lubricating oil is MoDTC (molybdenum dithiocarbamate) containing Mo and sulfur components. When MoDTC is used as a lubricating oil, the alloy film 3 does not necessarily contain Mo, but preferably contains Mo. The resulting tribofilm is a nanometer-scale molecular film that prevents direct contact between solids in relative motion and reduces the shear resistance of the solid surface. The state in which lubricity is imparted by the tribofilm is called boundary lubrication.

In the alloy film 3, the total content of Mn and Mo is within the range of 2% by mass or less, regardless of whether the lubricating oil contains Mo. In the examples described later, when the alloy film 3 contains one or both of Mn and Mo, when the total content of Mn and Mo is within the range of 2% by mass or less, low friction and toughness are obtained. This indicates that an excellent alloy film 3 can be obtained. Mn is considered to act to increase the toughness and wear resistance of the alloy film 3 . Mo is believed to act to improve strength and hardness at high temperatures.

When focusing only on the contents of Mn and Mo, regardless of whether or not the lubricating oil contains Mo, when the alloy film 3 contains only Mn, the Mn content is 2% by mass or less, and Mo When only Mn is included, the content of Mo is preferably 2% by mass or less, and when both Mn and Mo are included, the total is preferably 2% by mass or less. By setting the total content of Mn and Mo within this range, the alloy film 3 can be made to have low friction and excellent toughness, as shown in Examples below. More preferably, the total content of Mn and Mo is 2% by mass or less, and more preferably 1% by mass or less, in order to achieve low friction and excellent toughness. Although the lower limit of the total content of Mn and Mo is not particularly limited, it can be about 0.1% by mass.

In the alloy film 3, the content of B other than Mn and Mo is preferably in the range of 0.1% by mass or more and 1.5% by mass or less. B is dissolved in Cr—N and has the effect of refining crystals. An alloy film containing B has increased toughness and improved wear resistance. In addition, as described above, B is thought to have the effect of facilitating the formation of a tribofilm made of molybdenum disulfide on the surface of the alloy film. A more preferable range of the B content is 0.2% by mass or more and 1.0% by mass or less, and a more preferable range is 0.2% by mass or more and 0.5% by mass or less. . By containing B in a preferable range, higher wear resistance can be exhibited.

The alloy film 3 preferably contains V and Ti. In this case, it is preferable that the V content is in the range of 0.05 mass % or more and 1 mass % or less, and the Ti content is in the range of 0.05 mass % or more and 1.5 mass % or less. V has the effect of forming fine nitrides to improve toughness and heat resistance. An alloy film containing V can improve durability in an environment with poor lubrication. Ti forms fine nitrides to strengthen the fabric. A more preferable range of V content is 0.1% by mass or more and 0.5% by mass or less, and a more preferable range of Ti is 0.1% by mass or more and 0.5% by mass or less. is within. By containing V in a preferable range, higher wear resistance can be exhibited. In addition, when Ti is included in the preferred range, it contributes to strengthening the base of the coating in the alloy coating, and the wear resistance can be further improved. If V and Ti exceed the respective upper limits, the friction performance deteriorates.

The N content constituting the alloy film 3 is preferably in the range of 30% by mass or more and 40% by mass or less.

The composition of the alloy film 3 was determined by elemental analysis using a glow discharge optical emission spectrometry (GD-OES method). In this GD-OES method, conductive and non-conductive films are high-frequency sputtered in an Ar glow discharge region, and the emission lines of the sputtered atoms in the Ar plasma are continuously spectroscopically observed in the depth direction of the thin film. It is a method to measure the elemental distribution of In the examples described later, a Marcus-type high-frequency glow discharge luminescence surface analyzer (rf-GD-OES) manufactured by Horiba, Ltd. was used. The measurement at that time is normal sputtering (in an argon atmosphere), the measurement range is 4 mm in diameter, the sample is cut into 7 mm squares, embedded (embedded) in indium, and depth analysis is performed by the GD-OES method. rice field.

The alloy film 3 is usually formed on at least the outer peripheral sliding surface 11 of the piston ring 10 by a PVD (physical vapor deposition) method. Examples of the PVD method include an ion plating method, a vacuum deposition method, a sputtering method, and the like.

As shown in FIG. 2, the alloy film 3 formed in this manner consists of a first alloy film (also referred to as an intermediate film) 3a provided on the substrate side and a second alloy film provided on the first alloy film 3a. An alloy film (also referred to as a dense film) 3b can be used. In particular, it is preferable that the intermediate coating 3a on the substrate side of the piston ring is more porous than the dense coating 3b on the surface side (sliding surface side). This intermediate film 3a acts to relieve the stress between the alloy film 3 on the surface side and the base material or the underlying layer, thereby improving the adhesion of the dense film 3b and suppressing cracking and peeling of the dense film 3b. has the advantage of being able to The composition of the porous intermediate coating 3a on the substrate side is the same as the composition of the dense coating 3b on the surface side, and can be formed by adjusting the film forming conditions. Such an intermediate film 3a may have a constant composition in the thickness direction, or may have a composition that varies in the thickness direction, and the thickness thereof is not particularly limited. and preferably 3 μm or more and 8 μm or less.

[Young's modulus of dense coating + Young's modulus of substrate] ÷ 2 × 0.92 ≤ [Young's modulus of intermediate coating] ≦[Young's modulus of dense coating+Young's modulus of substrate]÷2×1.08. By satisfying this relationship, the stress concentrated on the interface between the alloy film 3 and the base material 1 can be dispersed throughout the film, resulting in excellent toughness.

The alloy coating 3 is preferably composed of an intermediate coating 3a and a dense coating 3b as shown in Examples 1 to 13 described later. may be configured.

The porous intermediate film 3a on the substrate side and the dense film 3b on the surface side can be easily analyzed by image analysis using a cross session polisher (CP). They can be controlled, for example, by varying the bias voltage and nitrogen gas pressure. Although not particularly limited, as an example, the nitrogen gas pressure in the chamber is maintained at 6 Pa, the bias voltage is set to 0 V to -7 V when forming the porous intermediate film 3a, and the dense film 3b is formed. can be formed with a nitrogen gas pressure of 4.5 Pa and a bias voltage of -7V to -30V.

Although the thickness of the alloy film 3 is not particularly limited, it is preferably in the range of 3 μm or more and 50 μm or less, and more preferably in the range of 10 μm or more and 35 μm or less. The hardness of the dense coating 3b on the surface side of the alloy coating 3 is preferably in the range of 1400 or more and 2000 or less, preferably 1600 or more and 1800, in terms of Vickers hardness (JIS B 7725, ISO 6507) HV (0.05). It is more preferable to be within the following range. The hardness of the intermediate film 3a on the substrate side is preferably in the range of 800 or more and 1600 or less, more preferably in the range of 1200 or more and 1500 or less in HV (0.05). Vickers hardness can be measured using a micro Vickers hardness tester (manufactured by Futuretech Co., Ltd.) or the like, and "HV (0.05)" means Vickers hardness under a load of 50 gf. there is The Vickers hardness in Examples described later is the result of measurement with this micro Vickers hardness tester.

(Applicable fuel)
The piston ring 10 according to the present invention can improve the low friction performance of the alloy film 3 formed on the sliding surface and improve the wear resistance performance, especially when actually sliding with lubricating oil. It has lower friction and superior toughness than the wear-resistant coating, and has the effect of being able to suppress the occurrence of cracks and peeling.

As described above, the combination of the sliding member 10 and the lubricating oil 56 according to the present invention has the alloy film 3 excellent in low friction performance on the sliding surface 11, and during actual sliding with the lubricating oil 56 , a tribofilm made of molybdenum disulfide is formed on the sliding surface 11 of the alloy film 3 . As a result, the low friction performance can be improved and the wear resistance performance can be improved. Furthermore, since the combination of the sliding member 10 and the lubricating oil 56 according to the present invention can have low friction and excellent toughness, adhesion, cracking, and peeling are unlikely to occur.

The sliding member used in the combination according to the present invention (combination of the sliding member and the lubricating oil used when the sliding member slides) can constitute a use invention by itself. That is, the sliding member 10 used under lubricating oil containing Mo has a Cr—B—(Mn, Mo)—N-based alloy film 3 provided on the sliding surface 11, and the alloy The film 3 contains one or both of Mn and Mo, and the total content of Mn and Mo is in the range of 2% by mass or less, and the sliding used under lubricating oil not containing Mo. A moving member 10 having a Cr—B—(Mn, Mo)—N-based alloy film 3 provided on a sliding surface 11, and the alloy film 3 contains at least Mo among Mn and Mo. , the total content of Mn and Mo is within the range of 2% by mass or less. The configuration and effects of these sliding members 10 are the same as the combination according to the present invention (the combination of the sliding member and the lubricating oil used when the sliding member slides).

Hereinafter, the combination of the sliding member and the lubricating oil according to the present invention will be described in more detail with examples and comparative examples of piston rings.

[Examples 1 to 13 and Comparative Examples 1 to 10]
As the base material 1, C: 1.00% by mass, Si: 0.25% by mass, Mn: 0.3% by mass, Cr: 1.5% by mass, P: 0.02% by mass, S: 0.02 % by mass, remainder: JIS standard SUJ2 material equivalent to iron and inevitable impurities was used. The substrate 1 was preliminarily subjected to ultrasonic cleaning in an organic solvent liquid.

Next, an alloy film 3 was formed on the substrate 1 . The film was formed by using an arc ion plating apparatus, using a target whose composition was adjusted so as to obtain a predetermined alloy film composition after film formation, and arc discharge was generated on the surface of the target. In addition, nitrogen gas is introduced into the arc discharge chamber, and if necessary, a predetermined amount of inert gas (here, argon gas) is introduced, and a bias voltage of 0 to −30 V is applied to the alloy film 3. was formed to have a thickness of 20 μm. The alloy film 3 obtained here is composed of a porous intermediate film 3a on the substrate side and a dense film 3b on the surface side. The porous intermediate film 3a on the substrate side is formed with a thickness of 5 μm at a bias voltage of 0 V, and the dense film 3b on the surface side is formed with a nitrogen gas pressure of 4.5 Pa and an average bias voltage of −16 V to a thickness of 20 μm. It is what I did. The composition shown in Table 1 is the composition of the dense coating 3 b of the alloy coating 3 . Although the composition of the intermediate coating 3a is not shown in Table 1, it is omitted because it matches the composition of the dense coating 3b.

[Examples 1' to 13' and Comparative Examples 3' to 10']
In Examples 1 to 13 and Comparative Examples 3 to 10, the alloy coating 3 was composed only of the dense coating 3b with a thickness of 20 μm without forming the intermediate coating 3a. Alloy films of Examples 1' to 13' and Comparative Examples 3' to 10' were prepared in the same manner as above.

[Characteristic evaluation]
(Nano scratch test)
A nano-scratch test was performed. FIG. 3 is a configuration principle diagram of the nano-scratch tester used in the measurement of the friction coefficient, (A) is a measurement mode on the sliding surface 53, and (B) is a measurement mode on the non-sliding surface 54. is. FIG. 4 is an explanatory diagram showing the SRV test performed before measurement with the nano scratch tester and the subsequent processing procedure, (A) is the state during the sliding test, and (B) is the state after the test. and (C) is the state after removing the lubricating oil. The results are shown in FIGS. 7 to 11. FIG. First, the alloy films 3 of Example 4 and Comparative Examples 1 to 3 were formed on the surface of the substrate 1 (corresponding to JIS SUJ2 material) having a disk diameter of 24 mm by the same film forming means as described above. The resulting test sample was subjected to an SRV test (Schwingungs Reihungund und Verschleiss/frictional wear test) shown in FIG. The test conditions were as follows: SRV test equipment (see FIG. 4(A)) was used as the test equipment, balls made of SUJ2 steel (JIS G4805, high carbon chromium bearing steel) with a diameter of 10 mm were used, the load was 20 N, the frequency is 20 Hz, the sliding distance is 5 mm (sliding distance), the test time is 60 minutes, the test temperature is 80 ° C., and the lubricating oils are Strong Save X0-W20 (with MoDTC) and 0W-16 (without MoDTC). It was used.

A tribofilm shown in FIG. 4B was formed on the sliding portion (tribofilm forming portion) 53 by the friction wear test shown in FIG. 4A. After that, as shown in FIG. 4(C), the lubricating oil 56 was removed. The coefficient of friction of the test piece thus obtained was measured with a nano-scratch tester (Tribo Indenter manufactured by Hysitron) shown in FIG. The nano-scratch test was performed by bringing an indenter 52 attached to a cantilever 51 into contact with the surface of the test piece with a predetermined load and moving it in the direction of the arrow (see FIG. 3). The measurement conditions were as follows: Conical (tip radius 0.5 μm) was used as the indenter 52, hexane cleaning (ultrasonic cleaning) was performed as pretreatment, loads were 5 μN, 10 μN, 20 μN, and 50 μN, and the scratch distance was 0.4 μm. The scratch time was set to 10 seconds. The measurement was performed on both the sliding portion 53 and the non-sliding portion 54 of the ball 55 for the test piece obtained in FIG. 4, and the coefficient of friction at each portion was measured. 7 to 11 show the difference between the friction coefficient of the sliding portion 53 and the friction coefficient of the non-sliding portion 54 ([friction coefficient of sliding portion]−[friction coefficient of non-sliding portion]=friction coefficient difference A ) is a graph showing the results (Table 2) obtained by changing the test load.

FIG. 7 shows the results of a nanoscratch test of the alloy film of Example 4 with a lubricating oil containing Mo, and FIG. 8 shows the results of a nanoscratch test of the alloy film of Example 4 with a lubricating oil that does not contain Mo. This is the result. 7, the friction coefficient difference A is negative for all of 5 μN, 10 μN, and 20 μN, indicating that the sliding portion 53 has a lower friction coefficient than the non-sliding portion 54 . From this result, it was considered that a tribofilm made of molybdenum disulfide with a low coefficient of friction was formed on the sliding portion 53 . Then, it was considered that the tribofilm was produced by a chemical reaction between the sulfur component contained in the lubricating oil 56 and Mo contained in the alloy film 3 and/or the lubricating oil 56 . Further, in the results of FIG. 8, although Mo is not contained in the lubricating oil 56, similar to the results of FIG. It can be seen that the friction coefficient of the sliding portion 53 is lower than that of the sliding portion 54 . From this result, it was considered that a tribofilm made of molybdenum disulfide with a low coefficient of friction was formed on the sliding portion 53 . Then, it was considered that the tribofilm was produced by a chemical reaction between the sulfur component contained in the lubricating oil 56 and Mo contained in the alloy film 3 . From the results of FIGS. 7 and 8, it is understood that Mo should be contained in either or both of the alloy film 3 and the lubricating oil 56, and is preferably contained in both. By doing so, a tribofilm made of molybdenum disulfide can be formed on the sliding surface 53, thereby improving the low friction performance and the wear resistance performance.

FIG. 9 shows the results of a nano-scratch test of the alloy film of Comparative Example 1 with a lubricating oil containing Mo, and FIG. 10 shows the results of a nano-scratch test of the alloy film of Comparative Example 2 with a lubricating oil containing Mo. FIG. 11 shows the results of a nano-scratch test of the alloy film of Comparative Example 3 using a lubricating oil containing Mo. From the results of FIG. 10 , when the alloy film 3 contains boron, the friction coefficient difference A is negative for all of 5 μN, 10 μN, and 20 μN, and the sliding portion 53 is greater than the non-sliding portion 54 . It can be seen that the coefficient of friction is low. From this result, it was considered that a tribofilm made of molybdenum disulfide with a low coefficient of friction was formed on the sliding portion 53 . Since the alloy film does not contain Mo, it was considered that the tribofilm was generated by a chemical reaction between the sulfur component and Mo contained in the lubricating oil 56 . On the other hand, from the results of FIG. 9, when the alloy film 3 does not contain boron, the friction coefficient difference A is positive at all loads, and the tribofilm made of molybdenum disulfide is formed on the sliding portion 53. thought not to have been generated. The difference between the results of FIGS. 9 and 10 is whether or not the alloy film 3 contains boron. Therefore, it can be seen that the boron contained in the alloy film 3 has the effect of facilitating the generation of molybdenum disulfide in the sliding portion 53 .

FIG. 11 shows the results of a nano-scratch test of the alloy film of Comparative Example 3 using a lubricating oil containing Mo. 11 and FIG. 10, when the alloy film 3 contained titanium and vanadium, the friction coefficient difference A was positive at all loads. At this time, it is not clear whether a tribofilm made of molybdenum disulfide is formed on the sliding portion 53 or not, but it is considered to be formed from the results of FIG. However, since the friction coefficient difference A is positive, it is considered that the inclusion of titanium and vanadium increased the friction coefficient.

Note that the results of Example 4 in FIG. 7 show that the content of titanium is about 1/10 and the content of vanadium is about 1/2 as compared to the alloy film (Comparative Example 3) in FIG. Furthermore, it is the result of the alloy film 3 containing manganese and Mo. When the results of FIG. 7 and the results of FIGS. 10 and 11 are compared and considered, in order to generate a tribofilm with a low coefficient of friction made of molybdenum disulfide, the Cr—N alloy film must contain at least B. including one or both of Mn and Mo when used under a lubricating oil containing Mo, and containing at least Mo of Mn and Mo when used under a lubricating oil that does not contain Mo is considered desirable. When titanium and vanadium are contained in order to improve wear resistance and the like, it can be said that it is desirable to specify the content and contain them within a range in which the friction coefficient difference A is negative.

(adsorption force measurement)
Adsorptive force measurements were performed. FIG. 12 is an explanatory diagram of adsorption force measurement by an AFM (atomic force microscope), and FIG. 13 is a graph showing the adsorption force measurement results. In the measurement, the alloy films 3 of Example 4, Comparative Example 1 and Comparative Example 2 were used as test samples. As measuring devices, Nanoscope V and Dimension ICON manufactured by Bruker AXS were used. The measurement conditions were Peak Force QNM mode, hexane cleaning (ultrasonic cleaning) was performed as pretreatment of the test sample, the measurement field was 500 nm square (500 nm x 500 nm square area), and the measurement environment was an argon atmosphere. For each test sample, the adsorption force was measured at a 500 nm square, and the average value over the entire surface was calculated. The calculated value of Comparative Example 1 is defined as 1 (reference value), and the relative value with the calculated values of Comparative Example 2 and Example 4 is shown in FIG. 13 as the "adsorption force ratio".

From the results of FIG. 13, the adsorption force ratio of Comparative Example 2 was 0.342, but the adsorption force ratio of Example 4 was 0.040, which was extremely small. This result clarifies that the surface of the alloy film 3 of Example 4 can reduce the adhesion of abrasion powder generated during sliding due to the small adsorption force ratio, and the friction due to adhesion can be reduced. increase can be prevented.

(Abrasion test)
The wear test was conducted by the roller tip type wear test method shown in FIG. A measurement sample 31 (length 7 mm, width 8 mm, height 5 mm) obtained under the same conditions as the piston rings obtained in Examples 1 to 13 and Comparative Examples 1 to 10 is used as a fixed piece, and a counterpart member 32 (rotary piece). A doughnut-shaped sample (outer diameter: 40 mm, inner diameter: 16 mm, thickness: 10 mm) was used. The friction coefficient test conditions using each measurement sample 31 are lubricating oil 33: machine oil (kinematic viscosity is 1.01 at 100 ° C. and 2.2 at 40 ° C.), oil temperature: room temperature, rotation speed: 200 rpm, load : 588 N, test time: 3 hours. The oil dropping rate from the dropping tube 34 was set to 0.04 mL/min. The mating member 32 made of boron cast iron is ground into a predetermined shape, and then subjected to surface grinding sequentially by changing the fineness of the grinding wheel. conforming to JIS B0601 (2001)).

The test results are shown in Table 3 as wear ratios. The wear ratio was expressed as a ratio when the wear amount of Comparative Example 1 was set to 1. When the wear ratio is less than 1, the wear resistance is higher than that of Comparative Example 1. All of the alloy films (Examples 1 to 13) within the composition range according to the present invention exhibit high wear resistance with a wear ratio of less than 1, and more preferred Examples 4 to 6 have a wear ratio of 0.30. It ranged from ~0.32. In addition, Table 3 further includes "film hardness (Vickers hardness)", "hardness ratio" to the film hardness of Comparative Example 1, and "scratch ratio (intermediate film + dense Film)”, and “toughness evaluation value” obtained by multiplying the hardness ratio and the scratch ratio. The Vickers hardness was measured using the described micro Vickers hardness tester (manufactured by Futuretech Co., Ltd.).

(Scratch test)
The scratch test was performed using the scratch tester shown in FIG. In the scratch test, the limit load at which film peeling occurs was determined, and the scratch ratio (peeling resistance load ratio) representing the peeling resistance was evaluated. The scratch test is a test method for a force applied in parallel (horizontal) to the sliding surface on which the film is formed, and the scratch test device 20 shown in FIG. ) was performed using The scratch test apparatus 20 shown in FIG. 6 presses an indenter 21 from above a sample 23 (13 mm×13 mm×5 mm in thickness) placed on a table 22, moves the sample 23 in that state, and at that time AE (acoustic Emission) detector 24 for detection. Here, load loading speed: 100 N / min, table speed: 10 mm / min, AE sensitivity: 1.2, indenter tip: R0.2 mm, test load: 0 to 100 N, test distance: 5 mm, test piece material: SKH51 Measured under conditions. For the evaluation, the peeling load (scratch load) was taken as the load when the occurrence of AE was detected by the scratch test.

The scratch ratio (peeling load resistance ratio) was expressed as a relative ratio of the scratch load of Examples 1 to 13 and Comparative Examples 2 to 10 to the scratch load of Comparative Example 1, and the results are shown in Table 3. Furthermore, the scratch load of Examples 1' to 13' and Comparative Examples 3' to 10' was expressed as a relative ratio "scratch ratio (only dense coating)" to the scratch load of Comparative Example 1, and the results are shown in Table 4. As the scratch ratio is larger than 1, the scratch load is large and the peeling resistance is high. As shown in Tables 3 and 4, the peel resistance of Examples 1 to 13 and Examples 1' to 13' is excellent, and Examples 4 to 6, 12, 13 and Examples 4' to 6', 12' and 13' were particularly excellent in peeling resistance. Comparing the alloy coating 3 comprising the intermediate coating 3a and the dense coating 3b with the alloy coating 3 comprising only the dense coating 3b, the former (alloy coating 3 comprising the intermediate coating 3a and the dense coating 3b) has a higher scratch ratio. rice field. This result shows that the separation resistance is enhanced by providing the intermediate coating 3a as the lower layer of the dense coating 3b.

In the examples exemplified here, B content: 0.3 to 0.4 mass%, Ti content: 0.24 to 0.48 mass as a more preferable content range (total total 100%) %, V content: 0.14 to 0.35% by mass, Mo and/or Mn content: 2% by mass or less in total, N content: 30 to 40% by mass, and Cr as the balance.

REFERENCE SIGNS LIST 1 base material 2 base layer 2' nitride layer 3 alloy coating 3a first alloy coating (intermediate coating)
3b Second alloy coating (dense coating)
10, 10A, 10B, 10C piston ring 11 sliding surface (outer peripheral sliding surface)
12 Upper surface 13 Lower surface 14 Inner peripheral surface 20 Scratch test device 21 Indenter 22 Table 23 Sample 24 Detector 30 Abrasion tester 31 Measurement sample 32 Mating material 33 Lubricating oil 34 Drop tube 51 Cantilever 52 Indenter 53 Sliding portion 54 Non-sliding portion 55 Ball 56 Lubricant F Load

Claims (4)

A combination of a sliding member and lubricating oil used when the sliding member slides,
The sliding member has a Cr—B —Ti—V— (Mn, Mo)—N-based alloy film provided on the sliding surface, and the alloy film contains at least Mn among the Mn and Mo. Including, the total content of the Mn and the Mo is within a range of 2% by mass or less,
A combination of a sliding member and lubricating oil, wherein the lubricating oil contains Mo and sulfur components . A combination of a sliding member and lubricating oil used when the sliding member slides,
The sliding member has a Cr—B —Ti—V— (Mn, Mo)—N-based alloy film provided on the sliding surface, the alloy film containing the Mn and Mo, and the Mn and the total content of Mo is within a range of 2% by mass or less,
A combination of a sliding member and a lubricating oil, wherein the lubricating oil contains a sulfur component and does not contain Mo. The B content is in the range of 0.1% by mass or more and 1.5% by mass or less, the N content is in the range of 30% by mass or more and 40% by mass or less, and the V content is It is in the range of 0.05% by mass or more and 1% by mass or less, the Ti content is in the range of 0.05% by mass or more and 1.5% by mass or less, and the balance is Cr and inevitable impurities. A combination of the sliding member according to item 1 or 2 and lubricating oil. A combination of a sliding member and lubricating oil according to any one of claims 1 to 3 , wherein the sliding member is a piston ring for an internal combustion engine.

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